Phosphorescence is a type of photoluminescence related to fluorescence. When a phosphorescent substance is exposed to light of a shorter wavelength, it will absorb the light and reemit it at a longer wavelength, causing the substance to glow. Unlike fluorescence, the glow of phosphorescence does not stop immediately after the source of excitatory radiation is switched off, and an afterglow with durations of fractions of a second up to hours can occur. The energy absorbed by a substance during phosphorescence is released relatively slowly in the form of light. This process is used for glow-in-the-dark materials that are "charged" by exposure to light.
The term "phosphorescence" comes from the ancient Greek word φῶς (phos), meaning "light", and the Greek suffix -φόρος (-phoros), meaning "to bear", combined with the Latin suffix -escentem, meaning "becoming of", "having a tendency towards", or "with the essence of". The study of phosphorescent materials led to the discovery of radioactive decay.
Phosphorescence occurs when energy is supplied by electromagnetic radiation, usually ultraviolet light. Unlike fluorescence, phosphorescence does not re-emit the light immediately. Instead, it releases light very slowly in the dark due to its energy transition state/Spectroscopy/Electronic_Spectroscopy/Radiative_Decay/Phosphorescence). The absorbed energy usually goes through a high energy state, which happens to be the triplet state, and the energy gets trapped in the triplet state because its physical situation forbids the transition to return to a lower energy state/Spectroscopy/Electronic_Spectroscopy/Radiative_Decay/Phosphorescence). Materials that can produce phosphorescence often contain zinc sulfide, sodium fluorescein, rhodamine, or strontium/Spectroscopy/Electronic_Spectroscopy/Radiative_Decay/Phosphorescence).
